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New Celestrons and Hd type Corrector removal

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#1 mega256

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Posted 03 December 2012 - 08:09 PM

> Because it covers a wide field of view, the optical
> elements of the EdgeHD must meet centering and
> alignment tolerances considerably tighter than those of
> the classic SCT design. For example, because the cor‐
> rector plate must remain precisely centered, we secure
> it in place with alignment screws tipped with soft
> Nylon plastic. The screws are set on the optical bench
> during assembly while we center the corrector plate.
> Once this adjustment is perfect, the screws are tight‐
> ened and sealed with Loctite® to maintain the correc‐
> tor in position. This seemingly small mechanical
> change ensures that the corrector plate and the second‐
> ary mirror mounted on the corrector plate stay in per‐
> manent optical alignment.

Interesting Celestron white paper...

http://www.celestron...a=downloadfi...
>
>

#2 mega256

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Posted 04 December 2012 - 10:26 AM

After reading this WHITE PAPER ,looks like we should not back out the screws on the corrector plate when cleaning
the glass..Just be very awhear that the plastic tips on the
screws dont come off.

#3 Alph

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Posted 04 December 2012 - 12:41 PM

After reading this WHITE PAPER ,looks like we should not back out the screws on the corrector plate when cleaning
the glass..Just be very awhear that the plastic tips on the
screws dont come off.

That caught my attention too. I did not hear though from anyone having a problem with the corrector plate set screws.

#4 Eddgie

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Posted 04 December 2012 - 05:03 PM

Well, I have already had mine off. I did a post here many months ago to document the fact that I had to pull the corrector due to some fogging that had developed on the inside and at least one other person had to send their scope back to Celestron for this problem.

But I pulled mine myself and I had to back out the screws to do it.

I was easily able to recenter it though using a bright star and centering the Poisson Spot. Was quite easy to get it back into the right position.

The reason the screws needed to be removed was that the mirror was set in place with some form of semi-hard plastic (like a silicone RTV) at each screw point that expanded out in the space between the edge of the glass and the cell about 1/2 inch in either direction. I had to back out the screws quite a bit and cut through the stuff with an Exacto knife, and even then, I had to really pull hard on the corrector to get it to come out. I did not take any special precaution to count the turns or anything, but someone that knows this now could just make sure they turn out every screw some exact amount (Exactly one turn for exmaple).

Since then, someone on that thread said that Celestron no longer uses this stuff. I don't know if this is true or not, but mine had it for sure. Perhaps they broke a corrector trying to get it out or something and figured out it was a bad idea. I don't know, but I do know it was a bad idea.

Anyway, it is not a problem to re-align it. At least I didn't think so. I had mine back in position in about 5 minutes under the stars. Was easy.






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